Index for Section 3

Alphabetical listing for F

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fread(3)
NAME
  fread, fread_unlocked, fwrite, fwrite_unlocked - Perform input/output
  operations

SYNOPSIS
  #include <stdio.h>

  size_t fread(
	  void *pointer,
	  size_t *size,
	  size_t *num_items,
	  FILE *stream );

  size_t fread_unlocked(
	  void *pointer,
	  size_t *size,
	  size_t *num_items,
	  FILE *stream );

  size_t fwrite(
	  const void *pointer,
	  size_t *size,
	  size_t *num_items,
	  FILE *stream );

  size_t fwrite_unlocked(
	  const void *pointer,
	  size_t *size,
	  size_t *num_items,
	  FILE *stream );

LIBRARY
  Standard C Library (libc)

STANDARDS
  Interfaces documented on this reference page conform to industry standards
  as follows:

  fread(), fwrite():  XPG4, XPG4-UNIX

  Refer to the standards(5) reference page for more information about
  industry standards and associated tags.

PARAMETERS
  pointer
      Points to an array.

  size
      Specifies the size of the variable type of the array pointed to by the
      pointer parameter.

  num_items
      Specifies the number of items of data.

  stream
      Specifies the input or output stream.

DESCRIPTION
  The fread() function copies num_items of data of length size from the input
  stream into an array beginning at the location pointed to by the pointer

  r parameter.

  The fread() function stops copying bytes if an End-of-File or error
  condition is encountered while reading from the input specified by the
  stream parameter, or when the number of data items specified by the
  num_items parameter have been copied.	 The function leaves the file pointer
  of the stream parameter, if defined, pointing to the byte following the
  last byte read, if there is one. The fread() function does not change the
  contents of the stream parameter.

  The fwrite() function appends num_items of data of length size from the
  array pointed to by the pointer parameter to the output stream.

  The fwrite() function stops writing bytes if an error condition is
  encountered on the stream, or when the number of items of data specified by
  the num_items parameter have been written.  The fwrite() function does not
  change the contents of the array pointed to by the pointer parameter.

  The fread_unlocked() and fwrite_unlocked() functions are functionally
  identical to the fread() and fwrite() functions, except that
  fread_unlocked() and fwrite_unlocked() may be safely used only within a
  scope that is protected by the flockfile() and funlockfile() functions used
  as a pair. The caller must ensure that the stream is locked before using
  these functions.

NOTES
  If the stream parameter is invalid, the result of calling the fread(),
  fwrite(), fread_unlocked(), and fwrite_unlocked() functions is undefined.

RETURN VALUES
  Upon successful completion, the fread(), fwrite(), fread_unlocked(), and
  fwrite_unlocked() functions return the number of items actually
  transferred. If the num_items parameter is negative or 0 (zero), no
  characters are transferred, and a value of 0 (zero) is returned. If a read
  or write error occurs, the error indicator for the stream is set, and errno
  is set to indicate the error.

ERRORS
  Refer to the fgetc(3) reference page for error codes returned by fread()
  and fread_unlocked().

  Refer to the fputc(3) reference page for error codes returned by fwrite()
  and fwrite_unlocked().

SEE ALSO
  Functions: read(2), write(2), fopen(3), getc(3), gets(3), printf(3),
  putc(3), puts(3), scanf(3)

  Standards: standards(5)

Index for Section 3

Alphabetical listing for F

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